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Implementation and control of RF manipulations in the PS

Implementation and control of RF manipulations in the PS. H. Damerau, S. Hancock CERN/GSI Meeting on RF Manipulations and LLRF in Hadron Synchrotrons 21/03/2014. Overview. Introduction RF systems and nominal beam in the PS Symmetry of RF manipulations

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Implementation and control of RF manipulations in the PS

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  1. Implementation and control of RF manipulations in the PS H. Damerau, S. Hancock CERN/GSI Meeting on RF Manipulations and LLRF in Hadron Synchrotrons 21/03/2014

  2. Overview • Introduction • RF systems and nominal beam in the PS • Symmetry of RF manipulations • Injection and bucket numbering • Signals for RF manipulations • Drive RF and voltage program generation • Beam phase and radial loops • Effect of relative phase control • Ejection bucket numbering • Conclusions and future plans

  3. Overview • Introduction • RF systems and nominal beam in the PS • Symmetry of RF manipulations • Injection and bucket numbering • Signals for RF manipulations • Drive RF and voltage program generation • Beam phase and radial loops • Effect of relative phase control • Ejection bucket numbering • Conclusions and future plans

  4. Introduction PS Protons to fixed target experiments Protons from PSB • Protons and ions to SPS (and LHC) • Protons to AD and nTOFtarget Pb54+ (future: Ar11+, Xe39+) from LEIR • Beams from single bunch to 72 bunches, flexible longitudinal pattern • Intensity range from about 109 to 3 · 1013 particles per cycle • Major bunch shortening along the cycle, from 180 ns to 4 ns (45 times!) • Splitting and batch compression since long, but on dedicated cycles • Since 2011/2012: combinations of RF manipulations for LHC-type beams • Beam control hardware still based on mix: • Digital: All RF sources, local oscillators, etc. • Analog: Phase and radial position detection

  5. RF Systems to perform those manipulations RF Manipulations 2.8 – 10 MHz 40 MHz Acceleration to SPS PS 80 MHz 200 MHz Longitudinal blow-up and 200 MHz structure for SPS 13/20 MHz RF Manipulations  24 (+1) cavities from 2.8 to 200 MHz

  6. Nominal beams: triple split h = 7  21 • Established LHC beam generation scheme since 2000 • Triple splitting on flat-bottom • Acceleration on h = 21 • Double (50 ns) or quadruple (25 ns) splitting on flat-top 1.4 GeV 26 GeV/c 25 ns 26 GeV/c 50 ns Key harmonic for acceleration h = 21 with bunch rotation cavities at h = 84/168

  7. Higher complexity required for beams to LHC • More evolved RF manipulations are simple to simulate, • Initial simulation (rigid RF) • Measurement Ekin = 2.5 GeV Ekin = 2.5 GeV RF Manipulations for Higehr Brightness LHC-type Beams, IPAC13, pp. 2600-2602 • but what is needed to turn them from simulation to reality?

  8. Introduction Categories of RF manipulations: • Many RF manipulations require special care of bucket numbering

  9. Symmetry of RF manipulations Batch compression: hRF= 8  9 11 13 17 20 Splitting: hRF = 8  16 VRF, h16 VRF, h8 • All buckets different (even and odd harm.) • Works in each bucket • Periodicity: h = 8 • Periodicity: h = 1 • All RF sources should be synchronous with respect to frev

  10. Overview • Introduction • RF systems and nominal beam in the PS • Symmetry of RF manipulations • Injection and bucket numbering • Signals for RF manipulations • Drive RF and voltage program generation • Beam phase and radial loops • Effect of relative phase control • Ejection bucket numbering • Conclusions and future plans

  11. Triple splitting versus batch compression 3 4 2 1 3 4 2 1 1st injection 2nd injection More evolved beam control for batch compression than for triple splitting

  12. Injection bucket selection • Bunches from PSB must be placed into the correct buckets • Batch compression works only for even number of bunches 1 turn • Bucket number control during both transfers PSB  PS H. Damerau, S. Hancock, CERN/GSI Meeting on RF Manipulations and LLRF in Hadron Synchrotrons

  13. Synchronizing PSB and PS – 1st injection Tagged clock DDS h128 MHS DDS R. Garoby, Multi-harmonic RF Source for the Anti-proton Production Beam of AD, CERN PS/RF/Note 97-10 frev, closed loop RF directly to cavities (one DDS per cavity) … … Bucket number control • Sync. on h = 1, fix bucket # Inj. Bucket selection fRF, inj. = 9 · 436.568 MHz MHS h = 1 Shifted trains to PSB, 1st inj. MHS hPL = 9 • Lock f- loop on inj. synth. Generate synchronous h1, h4 and h8 for PSB, while locking f-loop on h9

  14. Synchronizing PSB and PS – 2nd injection Tagged clock DDS h128 MHS DDS R. Garoby, Multi-harmonic RF Source for the Anti-proton Production Beam of AD, CERN PS/RF/Note 97-10 frev, closed loop RF directly to cavities (one DDS per cavity) … … Bucket number control • Sync. on h = 1, fix bucket # Inj. Bucket selection MHS h = 1 Shifted trains to PSB, 2nd inj. MHS hPL = 9 Generate synchronous h1, h4 and h8 for PSB, while locking f-loop on h9

  15. Overview • Introduction • RF systems and nominal beam in the PS • Symmetry of RF manipulations • Injection and bucket numbering • Signals for RF manipulations • Drive RF and voltage program generation • Beam phase and radial loops • Effect of relative phase control • Ejection bucket numbering • Conclusions and future plans

  16. Example: control of cavities during BCMS • Batch compression: • Two active groups at harmonics h, h + 1 • 3rd group preparing for harmonic h+2 • Bunch merging: • Two active groups at harmonics 2h, h • 3rd group preparing for harmonic 3h • Triple splitting: • Three groups active: harmonics h, 2h, 3h

  17. Requirements for RF manipulations • Easy adjustment of each step of RF manipulation • Voltage programs and duration of manipulation steps • Control of relative RF phases per manipulation step • Operational flexibility • Easy maintainability of settings • Possible move of absolute time of (parts of) RF manipulation

  18. Distribution of signals to cavities • Two signals per RF cavity: • RF drive signal: frequency (harmonic number)andphase • Slow voltage program: analog  digital serial data, 400 kB/s • Twice 16 pulses to open/close gap relay short circuit • Simple implementation, e.g. 10 MHz RF cavity system • How to program these functions to keep control of control? Would be confusingly complex to program and maintain!

  19. Frequency: Fixed tuning circuits (1984-2013) Tuning-Groups: hA: 36, 46 hB: 51, 56, 66, 76, 81, 91 hC: 86, 96 Group 4: 11, test cavity → All cavities of group tuned to same frequency → Hard-wired structure of tuning groups → 40 kV in three groups

  20. Frequency: Fixed tuning circuits (2013-) Tuning-Groups: hA: 36, 46, 51 hB: 56, 66, 76, 81 hC: 81, 91, 96 Group 4: 11, test cavity → All cavities of group tuned to same frequency → Hard-wired structure of tuning groups → 60 kV in three groups

  21. Distribution of signals to cavities • Consequences of fixed tuning groups • Common harmonic number function per group • Common relative phase function per group • Twice 16 pulses to open/close gap relay short circuit • Simple implementation, e.g. 10 MHz RF cavity system • Further simplification? Still many functions and timings to maintain!

  22. Voltage program generation Global program Mapping from groups to cavities • voltage programs • gap relay timings 0…200 kV Global red. × 0…100% Modifier grp. 1 × Modifier grp. 2 × Modifier grp. 3 × Modifier grp. 4 × Modifier grp. 5 × Modifier grp. 6 × Modifier grp. 7 × Modifier grp. 8 × 0…100% Voltage programs to cavities: C11 C36 C46 C51 C56 C66 C76 C81 C86 C91 C96

  23. Voltage program generation Global program Mapping from groups to cavities • voltage programs • gap relay timings 0…200 kV Global red. × 0…100% Modifier grp. 1 × Modifier grp. 2 × • Hardware switching of functions and timings migrated to software • Rules to copy settings from groups to cavities • Integrated spare cavity selection mechanism for C11 • Virtual matrix Modifier grp. 3 × New Control Structure of the 10 MHz RF System in the CERN PS, CERN-ATS-Note-2013-021 TECH Modifier grp. 4 × Modifier grp. 5 × Modifier grp. 6 × Modifier grp. 7 × Modifier grp. 8 × 0…100% Voltage programs to cavities: C11 C36 C46 C51 C56 C66 C76 C81 C86 C91 C96

  24. Upgraded distribution of voltage programs • More flexibility thanks to renovated generation of voltage programs: so-called ‘matrix’ • New hardware to generate digital voltage program data for each cavity • 8 logical groups of cavities • Matrix functionality implemented in software • Commissioned and ready for start-up 2014 H. Damerau, S. Hancock, CERN/GSI Meeting on RF Manipulations and LLRF in Hadron Synchrotrons

  25. Distribution of signals to cavities • Two signals per RF cavity: • RF drive signal: frequency (harmonic number) and phase • Slow voltage program: analog  digital serial data, 400 kB/s • Twice 16 pulses to open/close gap relay short circuit • Simple implementation, e.g. 10 MHz RF cavity system • Programming complexity reduced to the requirement of each beam • LHC-type beams: typically 10+2 functions and 4 timings • Single bunch low-intensity beams: 4+2 functions and no timing Still some functions and timings to maintain!

  26. Connect timings with functions • Standard PS Complex (CO) function generator: • Stop function execution • Restart with timings • Algorithm for real-time function re-generation • Link between function and timing generations • Extensively used to control PS RF Function with restarts Real-time functions

  27. Glue logic for the control: linked timing … … … … • Timing tree structure assures coherence between harmonic number (tuning group)and voltage programs (matrix) • Timings in structures generic: dynamic reconfiguration with tree • Moving (part of) an RF manipulation ideally one timing change • All dependent timings and function automatically updated

  28. Overview • Introduction • RF systems and nominal beam in the PS • Symmetry of RF manipulations • Injection and bucket numbering • Signals for RF manipulations • Drive RF and voltage program generation • Beam phase and radial loops • Effect of relative phase control • Ejection bucket numbering • Conclusions and future plans

  29. Beam phase and radial loop • Phase: Compare defined spectral component at hPL of with cavity return vector sum (or synchronous signal) • Radial position: D/S division of defined spectral components of beam pick-up at hPL • Still semi-analog implementation: • Digital local oscillators, programmable to any sequence harmonic numbers, hPL • Analog conversion to IF (10.7 MHz or 21.4 MHz), limiting and analog phase comparison  Not bunch-by-bunch, average of several turns • Phase normalizer circuit for radial loop for large dynamic range • Phase and radial loops act on all RF harmonics simultaneously • Always closed H. Damerau, S. Hancock, CERN/GSI Meeting on RF Manipulations and LLRF in Hadron Synchrotrons

  30. Harmonics of beam phase loop • Choice of suitable harmonic for phase loop: spectral component of beam (WCM) along RF manipulation Relevant spectral components Pure h= 21 hPL h = 9 20/21 h = 20 9/20 h = 21 • Ekin = 1.4 GeV Pure h= 9 hPL = 9/20 20/21 • For hRF = 9  10  20  21 phase loop at hPL = 9  20  21 sufficient • Bunches must be displaced symmetrically for averaged phase loop

  31. Simulated cavity return for phase loop • Vector sum of cavity returns presently only available for certain harmonics (8, 14, 16, 21) • Synchronous slave DDS instead of return vector sumto simulate cavity return • Beam loading effects invisible to phase loop • Phase of simulated cavity return not affected by changes of drive phase • Fine for any harmonic number • Works even with zero voltage in cavities: hRF  hPL Tagged clock frev, closed loop DDS h128 MHS DDS RF to cavities … … MHS hPL To phase loop

  32. Overview • Introduction • RF systems and nominal beam in the PS • Symmetry of RF manipulations • Injection and bucket numbering • Signals for RF manipulations • Drive RF and voltage program generation • Beam phase and radial loops • Effect of relative phase control • Ejection bucket numbering • Conclusions and future plans

  33. Merging with empty bucket • Beam test to shorten batches from 12 to 3 bunches: empty • Flip all RF phases starting from hRF = 7 to avoid merging with empty bucket • Assure symmetry with respect to frevfor phase loop

  34. Beam on wrong side with respect to h = 1 • Batch expansion and splitting of Pb54+ ion beam for LHC: hRF 21 24 110 ms 158 ms PS 12 PS 14 16 • Batch expansion and splitting on both sides: all hRF even • Expected batch expansion becomes compression: first odd hRF • Total manipulation periodic with frev only

  35. Overview • Introduction • RF systems and nominal beam in the PS • Symmetry of RF manipulations • Injection and bucket numbering • Signals for RF manipulations • Drive RF and voltage program generation • Beam phase and radial loops • Effect of relative phase control • Ejection bucket numbering • Conclusions and future plans

  36. Ejection bucket numbering • Azimuthal position of 1st bunch ambiguous after RF manipulations • What is bucket/bunch number one? • But: Synchronous frev,PSsignal with reproducible phase to beam • ‘Re-numbering’ of buckets by shifting reference from SPS • Shift of external reference frev,PS adjustable in SPS bucket units • Synchronize external and beam synchronous frev,PS Thibault fRF,SPS frev,SPS Bucket number control Synchronize 420 Ejection bucket selection Reset beam control frev,PS(external) frev,PS(internal) 1 H. Damerau, S. Hancock, CERN/GSI Meeting on RF Manipulations and LLRF in Hadron Synchrotrons

  37. Ejection bucket numbering: convention • Independent from RF manipulation: • 1st bunch at fixed time position with respect to frev, SPS Bunch numbering convention PS-SPS frev marker from SPS Beam signal from wall current monitor • Only convention, but extremely useful • to switch between beams with different RF manipulations • to debug beam transfer between PS and SPS H. Damerau, S. Hancock, CERN/GSI Meeting on RF Manipulations and LLRF in Hadron Synchrotrons

  38. Summary • Recent LHC-type beams require more evolved RF manipulations • Sequences of: • Bunch splitting and merging • Batch compression and expansion • Buckets different during process  injection bucket control • Reduce number of control parameters involved  simplify operational maintainability • Harmonic and phase functions per tuning group • Voltage program group-to-cavity mapping • Flexible control matrix in software • Phase and radial loops closed, needs symmetric manipulation • Correct bucket number when synchronizing: fixed 1st bunch

  39. Outlook Pure batch compression • New after long shutdown: • Digital voltage programs per cavity • New tuning groups: 40 kV  60 kV • Distribution matrix based on software • Digital AVC and 1-turn delay loops for 10 MHz RF cavities  Damien • Coupled-bunch feedback  Letizia • Up to 16 phase loop harmonics • Even longer RF harmonic sequences Ekin = 2.5 GeV • Simulation • High brightness in few bunches • hRF = 9  10… 20  21 • 13 RF harmonics • 7 phase loop harmonic • More evolved RF manipulations to come

  40. THANK YOU FOR YOUR ATTENTION!

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